Effect of phosphorus loadings on the performance of Co-Mo/γ-Al2O3 in hydrodesulfurization of coal tar
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摘要: 以分步浸渍法在固定MoO3、CoO含量 (质量分数) 为13.50%、2.11%的条件下, 通过改变磷酸浓度, 制备了不同P负载量的Co-Mo/γ-Al2O3催化剂。考察了不同的P负载量催化剂对内蒙古赤峰中温煤焦油加氢脱硫性能的影响。并以NH3程序升温脱附 (NH3-TPD)、X射线衍射 (XRD)、X射线光电子能谱 (XPS) 等手段对催化剂的结构性质进行了表征。结果表明, 适宜的P负载量可减弱活性组分与载体间的相互作用, 利于活性组分均匀分散在载体表面, 改善了催化剂的还原、硫化性能和酸性分布, 从而提高了催化剂的加氢脱硫活性。当磷酸质量分数为4%时, 催化剂表现出最佳的加氢脱硫性能, 硫脱除率达到96.98%。不同P负载量Co-Mo/γ-Al2O3催化剂加氢脱硫活性对应的磷酸浓度顺序为:4% >2% >6% >1% >0 >8%。Abstract: With the fixed loadings of molybdenum oxide of 13.50% and cobalt oxide of 2.11%, respectively, the Co-Mo/γ-Al2O3 catalysts were modified by adding different mass concentration of phosphoric acid via separate-step impregnation method. The effect of different phosphorus loadings of catalysts on the hydrodesulfurization performance was studied using middle temperature coal tar from Chifeng, Inner Mongolia. The structural properties of catalysts were characterized by the temperature programmed desorption of NH3 (NH3-TPD), XRD, XPS and other methods. The results show that a proper loading of phosphorus can weaken the interaction between the support and the active components, improve the dispersion of active compents on the surface of support, and promote the reduction and sulfuration of the active components and the distribution of acid, which can improve the hydrodesulfurization performance of the catalysts. The catalyst prepared with the phosphoric acid of 4% concentration exhibits the highest hydrodesulfurization activity with the sulfur removal of 96.98%. The effect of mass concentration of phosphoric acid on the hydrodesulfurization activety of the prepared catalysts is in the order of 4% >2% >6% >1% >0 >8%.
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Key words:
- phosphorus modification /
- Co-Mo catalysts /
- coal tar /
- HDS
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表 1 催化剂的组成及含量
Table 1 Compositions and contents of catalysts
Catalyst Content of component w/% Impregnating solution (aq) MoO3 CoO P2O5 a b c P0 13.50 2.11 0 (NH4)6Mo7O24·4H2O Co (NO3)2·6H2O P1 13.50 2.11 1.04 H3PO4 (NH4)6Mo7O24·4H2O Co (NO3)2·6H2O P2 13.50 2.11 2.08 H3PO4 (NH4)6Mo7O24·4H2O Co (NO3)2·6H2O P4 13.50 2.11 4.16 H3PO4 (NH4)6Mo7O24·4H2O Co (NO3)2·6H2O P6 13.50 2.11 6.44 H3PO4 (NH4)6Mo7O24·4H2O Co (NO3)2·6H2O P8 13.50 2.11 8.83 H3PO4 (NH4)6Mo7O24·4H2O Co (NO3)2·6H2O a: the first-step impregnation; b: the second-step impregnation; c: the third-step impregnation 表 2 中温煤焦油的元素组成
Table 2 Chemical compositions of middle-temperature coal tar
Element C H N S O Content w/% 83.14 8.34 0.40 0.66 7.46 表 3 催化剂的孔结构
Table 3 Pore structure parameters of the catalyst
Catalyst γ-Al2O3 P0 P1 P2 P4 P6 P8 BET surface area A/(m2·g-1) 292.77 245.50 244.80 238.08 226.04 209.29 211.43 Pore volume v/(cm3·g-1) 0.67 0.50 0.51 0.47 0.50 0.45 0.48 Average pore diameter d/nm 9.11 8.22 8.28 8.49 8.77 9.03 9.12 表 4 催化剂的NH3-TPD酸量分析
Table 4 Acid amount analysis of catalysts by NH3-TPD
Catalyst Acid amount weak medium strong total γ-Al2O3 1.00 1.00 1.00 3.00 P0 0.94 1.11 0.75 2.8 P1 0.57 1.07 0.61 2.25 P2 0.66 1.10 0.63 2.39 P4 0.62 1.27 0.75 2.64 P6 0.72 1.22 0.56 2.5 P8 0.82 1.08 0.36 0.75 表 5 催化剂的硫化度
Table 5 Sulfuration degree of catalysts
Catalyst P0 P1 P2 P4 P6 P8 Mo4+/Mo 0.77 0.74 0.77 0.80 0.78 0.80 S/Mo 0.06 0.06 0.06 0.07 0.07 0.07 Co-MoS/Co 0.29 0.31 0.29 0.29 0.20 0.11 Co-ox/Co 0.34 0.36 0.44 0.41 0.46 0.49 表 6 煤焦油及加氢产物的GC-MS分析
Table 6 GC-MS analysis of coal tar and products
Composition Coal-tar P0 P1 P2 P4 P6 P8 Alkane 11.05 14.05 14.18 14.62 16.15 14.78 13.55 Cycloparaffin 0 24.04 23.93 24.96 25.71 24.36 19.54 Benzene 25.67 21.04 22.92 24.07 23.10 24.58 25.04 Naphthalenes 16.10 22.91 23.55 22.43 21.27 23.37 25.46 Phenols 28.93 0 0 0.09 0 0 0 Indene 4.81 10.56 9.69 9.28 8.66 8.88 10.23 Fluorene 3.67 2.15 1.6 1.78 1.43 1.43 1.48 Organic acids 0.11 0.67 0 0.39 0 0 0 Ketones 0.93 0 0.46 0 0 0 0 Eneyne 2.79 1.85 0.88 1.06 0.57 1.0 1.86 Aldehydes 0 0 0 0 0.88 0.88 0 Anthracenes 0.35 0.52 0.92 0 0.56 0.56 0 Phenanthrenes 0 1.73 1.57 1.31 1.16 1.66 1.34 Furans 1.59 0 0 0 0 0 0 Others 4 1.48 0.3 0.01 0.51 0.2 1.85 Total 100 100 100 100 100 100 100 -
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